The study addresses the challenge of developing vascular networks in microfluidic chips for the long-term culture of three-dimensional cell aggregates like spheroids, organoids, tumoroids, or tissue explants. Existing microfluidic devices often lack complexity and require intricate setups. The researchers introduce a platform to monitor and establish endothelial networks around mesenchymal and pancreatic islet spheroids, as well as blood vessel organoids derived from pluripotent stem cells. These networks form functional connections with the spheroids and vascular organoids, enabling intravascular perfusion for up to 30 days on-chip. The results demonstrate improved organoid growth, maturation, and function with this vascularization method. The developed microphysiological system serves as a viable organ-on-chip model for vascularizing diverse 3D tissues, paving the way for establishing perfusions in organoids using advanced microfluidics.